Melanin concentrating hormone (hereafter abbreviated as “MCH”) is a cyclic peptide hormone/neuro-peptide, which was for the first time isolated by Kawauchi, et al., in 1983 from sermon hypophysis [Nature, Vol. 305, 321 (1983)]. The hormone is known to functionally antagonize to melanin cell stimulating hormone in fishes, to cause concentration of melanin granules in melanophore and participate in body color change [International Review of Cytology, Vol. 126, 1 (1991); Trends in Endocrinology and Metabolism, Vol. 5, 120 (1994)]. Also in mammals, MCH-containing neuron nerve cells are localized in the hypothalamus lateral field and uncertain zone, but their nerve fibers are projecting over a very wide scope in the brain [The Journal of Comparative Neurology, Vol. 319, 218 (1992)], and MCH is considered to preside over various central functions in living bodies.
Hypothalamus lateral field is known of old as feeding center, and furthermore, recently molecular biological and pharmacological knowledges suggesting participation of MCH in controlling energetic homeostasis are being accumulated. That is, it has been reported that expression of mRNA, which is an MCH precursor, was accelerated in the brains of ob/ob mice, db/db mice, Ay/a mice and Zucker fatty rats which are model animals of hereditary obesity, and in the brains of fasted mice [Nature, Vol. 380, 243 (1996); Diabetes, Vol. 47, 294 (1998); Biochemical and Biophysical Research Communications, Vol. 268, 88 (2000); Molecular Brain Research, Vol. 92, 43 (2001)].
Acute ventricular administration of MCH to rats was observed to induce accelerated feeding activity [Nature, Vol. 380, 243 (1996)] and chronic administration invites obesity accompanied by polyphagy [Proceedings of the National Academy of Sciences of the United States of America, Vol. 99, 3240 (2002)]. Moreover, MCH precursor gene-deficient mice show reduced food ingestion or rise in oxygen consumption per body weight compared to wild type mice. Their low body weight due to decrease in body fat was observed [Nature, Vol. 396, 670 (1998)].
On the contrary, transgenic mice which express excessive MCH precursor develop obesity accompanied by polyphagy and insulin resistance [The Journal of Clinical Investigation, Vol. 107, 379 (2001)]. Consequently, it is suggested that MCH is an important factor for developing obesity and participates in diseases induced by metabolic disorders or respiratory diseases of which one of risk factors is obesity. Besides, MCH is known to participate also in anxiety-causing action, epilepsy, memory, learning, diuretic action, excretory action of sodium and potassium, oxytocin secreting action, reproduction and reproductive function [Peptides, Vol. 17, 171 (1996); Peptides, Vol. 18, 1095 (1997); Peptides, Vol. 15, 757 (1994); Journal of Neuroendocrinology, Vol. 8, 57 (1996); Critical Reviews in Neurobiology, Vol. 8, 221 (1994)].
MCH causes versatile pharmacological actions through MCH receptors which are present mainly in the central nervous system. As receptors of MCH, at least two types of type 1 receptors (MCH-1R or SLC-1) and type 2 receptors (MCH-2R or SLT) are known [Nature, Vol. 400, 261 (1999); Nature, Vol. 400, 265 (1999); Biochemical and Biophysical Research Communications, Vol. 261, 622 (1999); Nature Cell Biology, Vol. 1, 267 (1999); FEBS Letters, Vol. 457, 522 (1999); Biochemical and Biophysical Research Communications, Vol. 283, 1013 (2001); The Journal of Biological Chemistry, Vol. 276, 20125 (2001); Proceedings of the National Academy of Sciences of the United States of America, Vol. 98, 7564 (2001); Proceedings of the National Academy of Sciences of the United States of America, Vol. 98, 7576 (2001); The Journal of Biological Chemistry, Vol. 276, 34664 (2001); Molecular Pharmacology, Vol. 60, 632 (2001)].
Of those, the pharmacological action observed on rodents is induced mainly via MCH-1R [Genomics, Vol. 79, 785 (2002)]. Because MCH-1R gene-deficient mice chronically administered with MCH do not develop polyphagy or obesity, it is known that controlling of energy exchange by MCH is induced via MCH-1R. Furthermore, the deficiency of MCH-1R is known to promote the activity amount of mice [Proceedings of the National Academy of Sciences of the United States of America, Vol. 99, 3240 (2002)], and its participation in central diseases accompanied by behavioral disorders, for example, attention-deficit hyperactivity disorder, schizophrenia, depression and the like also is strongly suggested [Molecular Medicine Today, Vol. 6, 43 (2000); Trends in Neuroscience, Vol. 24, 527 (2001)].
It is also reported that an autoantibody to MCH-1R is present in serum of vitiligo vulgaris patients [The Journal of Clinical Investigation, Vol. 109, 923 (2002)]. Furthermore, expression of MCH-1R in certain species of cancer cells was reported, and in vivo expression sites of MCH and MCH-1R also suggest MCH's participation in cancer, sleep, vigil, drug dependence and digestive disorders [Biochemical and Biophysical Research Communications, Vol. 289, 44 (2001); Neuroendocrinology, Vol. 61, 348 (1995); Endocrinology, Vol. 137, 561 (1996); The Journal of Comparative Neurology, Vol. 435, 26 (2001)].
Functions of MCH are expressed upon it binding to MCH receptors. Therefore, when its binding to MCH receptor is inhibited, then expression of MCH action can be inhibited. In consequence, substances which are antagonists to binding of MCH with its receptor are useful as preventing or treating agents of those various diseases in which MCH participates, for example, metabolic disorders represented by obesity, diabetes, hormone disorder, hyperlipidemia, gout, fatty liver, hepatitis, cirrhosis; cardiovascular disorders represented by stenocardia, acute or congestive heart failure, myocardial infarction, coronary atherosclerosis, hypertension, renal diseases, electrolyte abnormality; central nervous system or peripheral nervous system disorders represented by bulimia, emotional disturbance, depression, anxiety, epilepsy, delirium, dementia, schizophrenia, attention-deficit hyperactivity disorder, memory impairment, sleep disorders, cognitive failure, dyskinesia, paresthesias, smell disorders, morphine tolerance, drug dependence, alcoholism; reproductive disorders represented by infertility, preterm labor and sexual dysfunction; and digestive disorders, respiratory disorders, cancer or pigmentation et al.
Conventional known melanin concentrating hormone receptor antagonists are described, for example, in WO01/21577 and WO01/82925. In particular, WO01/82925 discloses the following compounds as a melanin concentrating hormone receptor antagonist.

In this reference, an imidazopyridine ring is not exemplified for Ar, and compounds having a specific substituent in a specific site of an imidazopyridine ring as well as their production methods are not concretely disclosed therein. Accordingly, even those skilled in the art who have seen WO01/82925 could not readily reach the knowledge that the imidazopyridine compounds of the invention would have an excellent effect as a melanin concentrating hormone receptor antagonist.
Patent Reference 1: WO01/82925
Patent Reference 2: WO01/21577
The invention is to provide imidazopyridine compounds having an antagonistic effect to the binding of MCH to MCH-1R, and to provide preventing or treating agents comprising the compound for metabolic disorders such as obesity, diabetes, hormone disorder, hyperlipidemia, gout, fatty liver, hepatitis, cirrhosis; cardiovascular disorders such as stenocardia, acute or congestive heart failure, myocardial infarction, coronary atherosclerosis, hypertension, renal diseases, electrolyte abnormality; central nervous system or peripheral nervous system disorders such as bulimia, emotional disturbance, depression, anxiety, epilepsy, delirium, dementia, schizophrenia, attention-deficit hyperactivity disorder, memory impairment, sleep disorders, cognitive failure, dyskinesia, paresthesias, smell disorders, morphine tolerance, drug dependence, alcoholism; reproductive disorders such as infertility, preterm labor and sexual dysfunction; and other digestive disorders, respiratory disorders, cancer or pigmentation.